1. Field of the Invention
The invention relates to creating images by transmitting signals and sensing the effect of objects in the field of view on the signals.
2. Description of the Prior Art
Using available light and optical methods, popular video cameras and television receivers produce high quality pictures in the format of human vision in real time. Beamforming techniques emulate optical methods by transmitting and receiving signals with transducer arrays and processing such signals. These techniques are especially important where light fails to penetrate effectively. However, it is difficult to match quality of familiar television system images using such beamforming methods.
The beamformed television method, U.S. Pat. No. 5,598,206 (January 1997) Bullis, approaches this goal with a practical hardware configuration. It provides visual format images at a frame rate that enables motion viewing. A three dimensional variation, U.S. Pat. No. 5,966,169 (October 1999) Bullis, emphasizes a practical method to achieve fine grain range resolution to enable viewing from any arbitrary perspective. The three dimensional block acquisition enables tissue tracking, guidance of therapeutic instruments and monitoring of healing.
Beamformed television, as disclosed in U.S. Pat. No. 5,598,206 (January 1997) Bullis, used a pair of orthogonal linear arrays. One array was for transmitting signals and one array was for receiving signals. A system of intersecting beams resolved a scene, as required for visual format imaging. This method requires that beams be narrow in one dimension and wide in the other dimension. These beams were described as fan beams. They are asymmetrical about the beam axis. The linear array configuration efficiently produces such beams. However, efficient formation of a useful field of view leads to transducer However, efficient formation of a useful field of view leads to transducer spacing, on center, also called pitch, that results in grating lobe effects. The general idea was to utilize one dimension of each array to resolve one angular, or cross range dimension, of a scene and the other dimension of that array to suppress grating lobes. The two arrays together resolved both cross range dimensions and limited the field of view in these dimensions. A variation involved limited steering that moved the field of view.
Although the directive effects of transmit array and receive array are described in beam pattern terms, there are important differences in the actual beamforming processes. Receive beamforming simply means adjusting for arrival time and adding signals to focus the collection of received signals. Simultaneous receive beamforming is based on the same set of received signals, except differing sets of arrival time adjustments are applied to sense in different directions and at differing focal zones. With sufficient computing power, all possible receive beam directions and focal zones can be sensed in a single transmit and receive event. Transmit beamforming means arranging signals to cause signals to be transmitted in a time relationship that causes focus in a selected direction and focal zone. Parallel transmit beamforming degenerates unless there is a way to separate signals. However, a need for rapid acquisition requires a similar parallel process.
A coding method was utilized. This enabled simultaneous excitation at different angles and at different focal zones. This was the needed complementary counterpart to simultaneous receive beamforming.
A combination of these complementary processes, operating with arrays that are orthogonal, provides highly efficient resolution in two cross range, or angular, dimensions. The resolving system can be accomplished with arrays that are straight line arrangements of elements that are called linear arrays.
It was found that grating lobe suppression could be accomplished by utilizing the width dimension of the linear arrays. A widening method was disclosed that utilized multiple transducers in a transverse arrangement relative to the line of the array. A specified alternative was to widen the transducers in the transverse direction. These widening provisions tended to improve power handling and gain of the system but the disclosure, U.S. Pat. No. 5,598,206 (January 1997) Bullis, primarily discussed the grating lobe suppression effects. This prior disclosure noted that beam descriptions were inexact, especially in the near field. Thus, the possibilities of widening were not fully explored.
Three dimensional systems, U.S. Pat. No. 5,966,169 (October 1999) Bullis, were made practical by the step chirp method for resolving the range dimension of the field of view. This was found to be possible to operate in combination with the coding method and other features of the preceding invention, U.S. Pat. No. 5,598,206 (January 1997) Bullis.
The three dimensional method made medical imaging a compelling development project because it solved the fundamental problem of wide slice thickness that is inescapably the result of a narrow aperture that is the width dimension of the conventional, single array systems. The orthogonal array method was a leap ahead of industry efforts that are based on xe2x80x9c1.5Dxe2x80x9d methods. But it was a completely electronic scanning system. The industry tendency is to utilize the conventional architecture with mechanical scanning apparatus to acquire a three dimensional block of image data.
Because the architecture of the orthogonal array applications is so different from the conventional form, it became useful to use a differentiating term. Instead of calling this technology ultrasound, the name orthosound was chosen. This emphasizes the orthogonal relationships in the architecture and helps to convey that this is not a small improvement to the familiar form, but is a major change in system architecture with very substantial benefits.
However, there are deep penetration issues with medical imaging using orthogonal array technology. In the terminology of this disclosure, these issues are categorized as (1) signal to noise ratio effects, (2) signal to clutter ratio effects, and (3) waveform and wave-front distortion effects. Signal to noise ratio can be improved by increasing transmitted signal level. Signal to clutter ratio stays the same if transmitted signal level is changed. Both of these can be improved by improving resolution where signal to noise ratio benefits from improved gain and signal to clutter level improves because clutter sources are excluded from a given resolution cell. Clutter is distinguished from artifacts. Clutter is a general background level that shows no recognizable shape. It comes from reflection signals that overpower the system capability to discriminate. Artifacts are similar except they are objects in the image that are recognizable representations of real objects that are incorrectly brought into the field of view. A pixel of a display represents the composite signal strength of the scattering sources that are within an associated voxel. A voxel is a volume resolution cell. Distortion effects degrade the signal processing operations.
The important qualities of a system begin with the capability to resolve a voxel. The degree of noise and clutter that are represented in the voxel also determine system capability. Contrast must be sufficient that objects can be discerned in the presence of interference by the noise and clutter. However, a well resolved set of voxels can represent objects such that these objects can be recognized by a pattern that approximates their shape. This is a powerful system gain effect. Distortion of signal waveform and wave-front shape modifies the capability to resolve a voxel, causing reduction in signal level and reduction in capability to reject interference. Distortion effects also disturb patterns so that shapes are not adequately recognizable.
The term real time describes timeliness of the imaging operation, but it is not clearly or consistently used. It definitely does not mean a delay in processing such as developing a film. For viewing of moving objects, it means a frame rate comparable to television. It may mean that it is soon enough to allow adjustment of system parameters and re-examination of a patient without a return visit. Although not precise, it is a critical measure of the usefulness of a system in any given application.
Deep penetration applications result in deterioration of image quality or timeliness. The background of the present invention includes previous disclosures as well as limitations therein. It also includes capabilities from other fields that can be utilized and capabilities and methods that are utilized in the popular conventional systems.
Previous disclosures, U.S. Pat. No. 5,598,206 (January 1997) Bullis and 5,966,169 (October 1999) Bullis, used approximations in discussing near field effects. These effects are significant to medical imaging configurations so the near field beam shapes must be more precisely addressed.
Methods are well known to make transducers that are sub-divided so that a transducer is actually a collection of transducers that are driven with a common signal line. This is commonly done to free the transducer motion in a transverse direction so that displacement in the desired direction can occur by material distortion rather than compression. Diamond dicing saws are known tools for subdividing piezo-electric transducers. They are also used to fabricate arrays of multiple transducers by cutting up a larger piece of piezoelectric material. Various means are known for making electrical connections, include soldering, ultrasonic welding, and conductive composite materials.
It is well known to improve signal to noise ratio by integrating the results of repeated transmission. Such repeated operations of a given sensing system are considered obvious. This measure carries a penalty of slowing the frame rate of the system.
The patent U.S. Pat. No. 5,598,206 (January 1997) Bullis disclosed use of signal tones of finite duration as codes. This method provides a resolution that is inherent to the code form. With simple tone codes, the time resolution is equal to the duration. This effect can be thought of as a range gate effect where a particular resolution increment is acquired by the receiver system and becomes a sample of the signal. This signal sample represents reflected signal from a limited range extent. This previous patent did not address the ramifications of deep penetration imaging in highly attenuating tissue though it did note the trade-off between tone code time duration and the number of codes that could be used in the available system bandwidth.
Another design issue in deep penetration applications is that of maintaining the range resolution effectiveness at depth. The general practice in the medical ultrasound industry is to use simple, short pulses to ensonify the field of view. The equivalent frequency domain representation of such short pulses is a very broad band of energy. In deep penetration systems, the natural attenuation process will effectively filter out most of the energy, leaving the system with a reduced band of energy. This will result in a much degraded received pulse width.
A step chirp method of signal processing was previously disclosed, U.S. Pat. No. 5,966,169 (October 1999)Bullis, which provides fine grain range resolution using simple frequency codes. This method specifically included the capability to adjust for variations in frequency response of the system. However, it did not address the severe variations of attenuation as a function of frequency.
The medical ultrasound industry has been actively pursuing methods called harmonic imaging, that involve transmitting signals from an array on a frequency and receiving signals that are twice the frequency. Penetration depth is benefited since the transmitted signals are at a lower frequency so that the outward one way path is significantly less attenuated than the return path.
The harmonic received signals are not the product of simple reflection in a linear system. The observed fact of such harmonic signals indicates that processes take place that are related to the nature and condition of the tissue. Such effects are also observed in materials. Various mechanisms for generation of these harmonic like signals are possible, one of which is a nonlinear effect that is similar to passive intermodulation distortion in communication antenna reflectors. Greenleaf, Science, Apr. 3, 1998, Volume 280, pp.82-85, shows the effect of two separate frequencies that produce the sum and difference frequency signals. It appears that U.S. Pat. No. 5,086,775, (February 1992) Parker et. al., is also addressing this effect.
Contrast enhancement is widely known in the industry. This involves injecting suitable materials into the blood stream so that the contrast between the blood path and surrounding tissue is more visible in images.
Most commercial ultrasound systems implement beamforming in only one dimension. That resolves the azimuth, or horizontal, cross range dimension. These devices produce an image by using the range dimension information so that a visual format display is not possible. This is an adaptation of the general architecture of most radars and sonars, whether used for detection or imaging. This simple architecture is efficient, but it fails to effectively limit the elevation beamwidth, thus providing only crude capabilities to show small details and very coarse capability to locate objects in the elevation, or vertical, dimension.
Adaptation of the simple radar and sonar architecture is especially problematic because of the extreme, three dimensional clutter environment that is encountered in medical imaging. The fact that the elevation, or vertical, dimension is not resolved beyond the field of view limitation of the slice thickness means that the volume resolution cell, or voxel, is crudely formed. This voxel is greatly elongated compared to its azimuth and range dimensions. This means that all clutter signals from sources within a voxel are added to the desired signal from a small object that is within the voxel. An appropriate system design matches the voxel to the approximate size of the smallest object that needs to be sensed or the smallest degree of detail that needs to be discerned.
In spite of this limited architecture, much progress has been made in ultrasound imaging. Powerful computing machines are made in compact form. A wide range of transducer array forms are available and a typical system has several on hand to be used as needed. These are plugged in to a computing console, one at a time. Such arrays are simply called transducers in the terminology of the medical imaging industry.
Transducer array fabrication methods are highly refined in this industry and very small, very high frequency arrays are efficiently manufactured. Such fabrication methods are represented in U.S. Pat. No. 5,808,967 (September 1998) Yu, et. al. This disclosure also discusses methods of transmitting and receiving axially symmetric beams from a mosaic planar array form, with interconnection methods to make elements electrically independent.
Only primitive forms of three dimensional imaging are currently accomplished by mechanical scanning of instruments based on the conventional, single array, architecture. Not only is this a slow way to scan, but the ultimate results are fundamentally flawed by the voxel formation capabilities of the instrument utilized.
In spite of the architectural flaw and lack of three dimensional capability, much progress has been made in ultrasound imaging. Powerful computing machines are made in compact forms. A wide range of transducer forms are available and a typical system has several on hand to be plugged in and used as needed. These are plugged in to the console, one at a time.
Known fabrication and switching methods are represented in U.S. Pat. No. 5,808,967 (September 1988) Yu, et. al. Where methods are disclosed for making transducers electrically independent and independently transmitting and receiving of axially symmetric beams.
This architecture is also poor in supporting navigation processes. The lack of accurate position fixing capability in the elevation angle dimension is a basic failing of this architecture whether it be to guide airplanes, torpedoes, or the insertion of instruments to treat diseases.
X-ray equipment is utilized for breast cancer screening. This imaging modality is also a two dimensional process that collapses a three dimensional volume onto a two dimensional film or other form of detector. It forces the examiner to try to see through many layers of tissue. The standard of early detection in this field is to find a tumor when it is about 0.5 cm. Success rate for finding smaller tumors does not seem to be a subject of statistical studies.
A radiologist typically looks at x-rays from successive examinations. It is also common practice to compare images obtained with different imaging modalities. Examination of vast quantity of images becomes burdensome to radiologists. Computer methods exist to handle digitized x-ray images, whether these are acquired by scanning film or by direct electronic sensing.
There are software means to track detailed movements in dynamic environments such as radar systems operating against a large number of detectable targets, some hostile and some friendly. Such software requires three dimensional sensing if the environment is complex. There are also methods of comparing natural images and variations therein. Wavelet methods are known to be useful in allowing for natural variations in such comparisons.
There are existing methods and new methods being developed to eliminate diseased tissue, once it is located. Some of these methods have the capability to be highly selective in their effect so as to eliminate only the diseased parts. These include locally effective drugs, energy sources that burn out the diseased region, and precise surgical methods. A prior art method that involves a locally effective injection is disclosed in U.S. Pat. No. 5,902,582 (May 1999) Hung. To effectively insert an instrument, such as a needle, it is highly beneficial to know the exact angle to point the needle relative to the insertion point and then to be able to follow the movement of the needle tip as it approaches the desired spot. This type of guidance is not available with prior art imaging modalities.
It is common practice to monitor the progress of patients after treatment for disease.
It is common practice to efficiently treat early forms of skin cancer where the problem is observed and treated in a single office visit.
Comprehensive military systems are known that sense and track threat targets and friendly targets, control and guide weapons, and assess results.
Referenced documents, in entirety, are incorporated herein. They contribute to the description of the present invention, but in case of conflict, the present document takes precedence.
A general object is to enable deep penetration in attenuating bodies and to rapidly produce three dimensional images that can be efficiently processed to give complete perception of the three dimensional block of information.
An object is to provide a complete three dimensional imaging system for medical ultrasound imaging in human or other living bodies.
An object is to provide a comprehensive medical system apparatus with integrated capability to arrange image equipment in a variety of configurations and control operating modes to carry out a sequence of detection, diagnostic, and therapeutic procedures in a single on-line session.
An object is to provide hand held transducer array systems that allow practitioners to move imaging device to a chosen location on a patient""s body.
An object is to provide a small footprint sensor that will enable viewing access between ribs.
An object is to replace x-ray imaging devices with ultrasonic imaging devices.
An object is to provide imaging over the dimension of velocity.
An object is to provide improved power intensity levels and receive sensitivity.
An object is to provide improved signal to noise ratio.
An object is to provide a simplified, transverse plane, flat scanning capability.
An object is to provide superior slice imaging.
An object is to reduce the risk of fracturing transducer elements in normal use.
An object is to reduce size of the entry region into the body.
An object is to minimize acoustic wave energy in the body.
An object is to minimize peak acoustic pressure in the body.
An object is to suppress clutter in images.
An object is to correct for refraction effects.
An object is to enable aberration correction.
An object is to reduce pulse distortion in time domain forms of reflected signals, and correspondingly improve range resolution.
An object is to enable simplified range gating hardware.
An object is to provide a research tool to investigate the scattering levels and harmonic content of such scattering for various types of human tissue.
An object is to enable imaging with low acoustic power intensity levels to prevent damage to the subject of examination.
An object is to minimize thermal losses in the transmitting transducer.
An object is to control clutter interference.
An object is to provide high resolution in the range dimension in environments where there is strongly differing attenuation over the frequency band.
An object is to provide diagnostic information related to tissue characteristics and condition.
An object is to utilize contrast enhancement substances to enable deeper penetration imaging and to enable high resolution viewing and to enhance sensitivity to motions such as blood flow motion.
An object of the present invention is to image the velocity field of moving particles in bodies.
An object is to provide overlay capability to enable comparison of successive examinations and comparison with other imaging modality results.
An object is to track tissue changes so as to distinguish development of diseases.
An object is to utilize computers in examination of large quantities of images.
An object is to guide disease treatment procedure.
An object is to provide industrial process inspection capability that does not involve destruction of the object.
An object of this present invention is to provide a complete three dimensional imaging system for underwater exploration or other underwater operations.
An object of this present invention is to provide a ground penetrating radar system that has sufficient resolution to distinguish between objects of interest and natural objects.
An object of this present invention is to provide an air acoustic imaging system, with optional capability to penetrate the ground to search for articles of interest.
An object of this present invention is to enable real time navigating of mobile operations such that high speed operations are enabled.
An object of the present invention is to enable dynamic guidance of systems including pointing information in two angular dimensions.
An object is to emulate the effectiveness of bats and other animals in detecting and homing on objects and avoiding obstacles in high speed flight.
Further objects of the present invention will become apparent from a consideration of the drawings and ensuing description.
A system has been invented that provides deep penetration, collimated, three dimensional, real time, ultrasonic imaging of the internals of the human body with diagnostic sensing features and treatment enabling features. The apparatus is a flexible arrangement of arrays and associated medical equipment, with means to select operating configurations and to control operating parameters. Because the sensing configuration makes extensive use of orthogonal arrangements and to distinguish it from conventional ultrasound technology, this new technology is called orthosound imaging.
A powerful parallel computer architecture enables use of a variety of transducer array forms and signal systems. As with conventional ultrasound apparatus, arrays are plug in devices that are changed to fit needs.
Orthosound is a combination of prior beamformed television inventions, U.S. Pat. No. 5,598,206 (January 1997) Bullis and U.S. Pat. No. 5,966,169 (October 1999) Bullis with new features that provide deep penetration capabilities in environments where signals are strongly attenuated by the medium of propagation. The new features include a wide array configuration with sub-divided elements, switching to configure transmit or receive configurations, bracket gating, attenuation compensation, and signal modulation methods. The sub-divided wide array method provided geometric beam control, including a fully collimated capability, that has a variety of unexpected benefits. The new features not only improve signal strength, they also suppress interference and give improved diagnostic capabilities. Medical treatment features are enabled and enhanced at greater depth.
Like the previous inventions, a transmit array and a receive array are oriented to resolve two cross range dimensions and a sparse array method efficiently forms a desired field of view. These arrays are arranged to be orthogonal to each other, and each produces respective beams that are orthogonal to each other. This new architecture incorporates a transmit beam segment coding method that enables rapid acquisition and a step chirp method that enables efficient range resolution. The system includes a capability to choose between a variety of array forms and signal operations to meet examination requirements.
An improved penetration capability is achieved with wide arrays that produce semi-collimated beams. Such an array has superior power handling capabilities and improves signal to noise ratio.
Semi-collimated beams are beams that are collimated in one transverse dimension in the region of the field of view and focused in the other transverse dimension. An orthogonal combination of two semi-collimated beam systems produces a system function that is fully collimated. Flat arrays produce a rectangularly collimated system and the field of view is a rectangular block. This enables rectangular displays without adjustment by image data processing.
Rectangular collimation improves clutter rejection capabilities in conjunction with the fine grain range resolving capabilities of the signal system. An operator has the flexibility to tune the bistatic angle, which is the angle between the two arrays, to emphasize this effect.
A further benefit of rectangular collimation is a refraction control capability in water bath or water stand off implementations. A flattening window made of thin plastic material is a system component that causes the transition from water to human tissue to occur over a planar surface. In conjunction with this tool, the arrays are oriented so that the straight line elements of both arrays are parallel to the planar surface. Time delay adjustments for transmit signals and receive signals effectively correct the refraction.
Since the array width dimension is flat the array can be curved in the other dimension without requiring a doubly curved surface. This is a more easily manufactured configuration that provides an orientation of individual transducer elements to better encompass the field of view.
The collimated concept is made possible by near field effects that shape beams at ranges short of where diffraction effects become important. In this near field, beam shapes are determined by the shape of the radiating aperture and signal timing. To know the size and shape of an active wavefront is to know the shape of the beam that it is to subsequently trace out. An alternate semi-collimated transducer array form is characterized as causing cylindrical collimation in one dimension. Cylindrical collimation causes a field of view that diverges or converges with range. Cylindrical collimation involves concave or convex radiating wavefronts. Radiating surfaces are approximately shaped like the wavefront or they are shaped like a section from the inner or outer surface of a cylinder with electrical time adjustment to impart the respective wavefronts. In general, radiating surfaces are quite arbitrary since the electrical system can adjust for many physical shapes. Plug-in arrays utilize combinations of rectangular and cylindrical semi-collimated methods.
Cylindrical collimation of either type does not give the rectangular field of view benefits. The concave form modifies power handling and causes curved focal zones that enhance the interaction with range resolving features to reduce sidelobe effects. Convex wavefronts allow thinner transducer arrays for shape and size restricted applications.
Returning to the primary array form that is straight line elements arranged along a cylindrical surface, it was found to be useful to utilize a known process of sub-dividing transducer elements to improve radiating surface displacement. It was found that long, thin, transducers could also be sub-divided into sub-elements so as to make transducers more durable. It also improves electrical interfacing. Here the sub-elements are separately connected to amplifiers that operate in parallel. Parallel amplifiers utilize the same signal so that a single signal channel is still sufficient.
An increase in the number of amplifiers adds cost, but an advantage of sub-divided elements and separate amplifier circuits is that it makes possible a new diagnostic mode of operation, at low additional cost, where the field of view is subdivided by switching amplifiers on or off. Sub-beams are selectively created. The sub-elements individually have semi-collimated properties. Sub-beams are like the system semi-collimated beams, only thinner. This can be done with either or both transmit amplifiers and receive amplifiers. These are on-line system adjustment options that do not require changing transducers. It will significantly reduce effects of sidelobes from the opposite array. This provides a highly sensitive mode of operation that can be applied for diagnostic purposes when suspicious things are seen in a larger image.
Programmable range resolving modes include simple pulse, step chirp, and gated continuous wave. New combinations of these modes have significant benefits. Simple step chirp operations are not compatible with transmit beam segment coding methods.
Bracket gating is a hybrid combination of simple pulse methods and step chirp methods. In this hybrid method, system range resolution is ultimately determined by the step chirp process, but an earlier stage of coarse range resolution is provided by the bracket gate. Bracket gating is particularly important for deep penetration applications where short range signals are overwhelmed by long range signals. Bracket gating involves tones that are stepped in frequency, but tone duration is greatly reduced such that a short duration sampling window fully accepts reflections only from a single range and excludes earlier and later returns. The rejection effectiveness is gradual, but for return signals that completely miss the sampling window, the rejection is very strong. This limits clutter effects prior to analog to digital conversion of received signals. A short bracket gate reduces the unambiguous range to be resolved by the step chirp process, so it reduces the number of steps that must be used in that process. Tone duration is adjusted so that a balance is achieved between interference effects of clutter and interference effects of noise.
However, the use of narrow bracket gates leads to signal processing complexity in signal processing where coding is used to simultaneously acquire different focal zones. This situation is much improved by a staggered burst transmission program where transmit code tones are timed so that all codes arrive back at the receiver at about the same time. Even though the stagger causes overlap for differing ranges, it is only nominal overlap since wide aperture effects and field of view width cause tones to arrive that are spread out in time. The various ranges and angles represented by such tones are needed for effective signal processing. A sliding processing window is used to effectively capture full tones. This prevents poor quality decoding and poor quality receive beamforming.
Bracket gating is especially important in enabling small footprint array systems where short stand-off operation is desired. The step chirp process can still be utilized in this arrangement because of the bracket gate.
Another new feature is a modification of the step chirp process to prevent degradation of range resolution in deep penetration applications. The transmit signals are adjusted for each step of the step chirp to give increasing amplitude as frequency increases. This process compensates for the extreme variation of attenuation over the frequency band causing a received signal spectrum that transforms to a short pulse to enable well defined range resolution increments. In simple pulse mode operation, spectrum modification is applied to transmit pulses and signal samples are arranged in transmit signal memory to give a similar effect.
Deep penetration is enhanced by use of modulation effects. Modulation is a process that produces signals that have frequencies that are different from transmitted signal frequencies. This effect enables lower attenuation return paths. It also gives diagnostic capabilities since the modulation effects are variable depending on tissue condition. Both arrays of the original orthogonal configuration are operated as coded transmit systems and the difference frequencies arise at intersections of beams.
Three dimensional capabilities of the imaging system enable highly perceptive pattern recognition capabilities of the human eye and brain.
Where needed, the three dimensional capabilities also enable highly precise navigation and control of instruments to carry out treatment procedures.
Signal processing is carried out using parallel computing hardware with a network switch that enables parallel, high speed transfer of information between computers at high speed.
Image signals are displayed for direct evaluation, image data is processed to optimize viewing sensitivity, therapeutic measures are guided, and the system configuration is optimized in a comprehensive medical system that enables a sequence of detection, diagnosis, and therapeutic procedures in a single office visit.
The scope of the invention should be determined by the appended claims and their legal equivalents and not by the examples and variations given.
This disclosure is written in terminology for the system design engineer who is knowledgeable in a wide range of disciplines within the general electronic and physics professions. A variety of specialists is typically required to produce the detailed hardware, depending on the application. Construction involves separate disciplines that include skills in transducer design and manufacturing, computer architecture, analog and digital circuit design, and software.